1. Field of the Invention
This invention relates to the field of electric heaters, and more particularly to an electric heater having improved heating efficiency and safety aspects, and implemented as a reenforced compact structure.
2. Brief Description of the Prior Art
A variety of heaters are available on the current market, such as oil burning heaters, electric fan heaters, quartz heaters, convection heaters with round heating elements, PTC (ceramic) heaters, etc. Apart from oil burning heaters, all the others release radiant heat energy directly from infrared heating elements. Such heating elements can provide fast creation of heat, but also increase the danger of fire or electric shock.
Electric heaters of the prior art generally are constructed with an exposed glow bar or wire which produces all of the radiant heat of the heater, the glow bar or wire being mounted in the heater behind a grating or wire screen through which the radiant heat energy passes into the environment.
In some such prior art heaters, heat reflecting panels redirect rearwardly directed radiant heat energy back toward the front of the heater. In others, a fan is installed in the heater behind the glow bar or wire to force hot air in the vicinity of the heating element toward the front of the heater through the grating or wire screen.
In all such prior art heaters, there exists a very hot region in the vicinity of the heating element, increasing the risk of fire if the heater is tipped over or if a combustible material, such as a curtain, is drawn into contact or near contact with the heating element. Such heater construction also increases the risk of being shocked or even electrocuted by accidentally touching the heater element through the grating or wire screen.
Other characteristics of prior art heaters are problematical, such as having low to medium heat transfer rate, being structurally fragile, having unsafe (infrared) surface conditions, having a short life, having high surface temperatures (some greater than 600xc2x0 C.), having poor insulation characteristics, and being subject to damage by exposure to water.
The present invention provides a comprehensive and rational solution to the problems associated with prior art heaters and heater elements, while still retaining a very high level of conductivity of heat energy in a safe manner.
A heater constructed according to the present invention represents a safe electrical heat energy generator which comprises a heater unit equipped a set of systematically organized heat radiating metal fins. An important feature of the invention is its reenforced compact structure in which a heating element and the heat radiating metal fin arrangement are manufactured as a single heater unit structure.
In such a structure, a heating element is surrounded with an insulating layer and enclosed inside a central heat conductive tubing of the framework for the metal fin arrangement, thereby defining the major components of the heater unit. In this manner, the entire heater unit structure is the source of radiant heat energy, not simply the heating element itself.
That is, the heating element, confined within the central heat conductive tubing, transfers heat to the interior surface of the tubing which, in turn transfers heat to the arrangement of spaced heat radiating metal fins, thereby increasing the amount of heat release due to the large surface area of the plurality of spaced metal fins. The gaps between the metal fins enforce movement of air currents and thus heat the surrounding air efficiently and uniformly.
Because the electrical current of the system is confined to the heating element enclosed in a central heat conductive tube, there is no risk of getting shocked by touching the heater unit, since no current carrying elements are exposed.
Additionally, due to the combined large area of heat radiating surfaces and the uniform distribution of radiant heat from the heater unit by the arrangement of heat radiating metal fins, there are no hot spots along the entire extent of the heater unit which would cause igniting of objects in the near vicinity of the heater unit or even objects touching the heater unit fin structure.
Compared with other heater appliances on the market, the heater unit of the present invention effectively reduces the risk of fire and electric shock.
As to the application of the invention, the heater unit can be used as a direct heat energy generator, or as the heat energy provider for any other kind of appliance requiring a radiant heat energy source.
In a broad sense, the present invention overcomes the aforementioned negative attributes of prior art heaters by providing a compactly constructed unique heat distribution system to reduce excessive hot spots or regions in the heater, while producing efficient, safe, and uniform heat radiation into the environment, e.g., a room.
In accordance with one aspect of the invention, there is provided a heater comprising: a housing; a heater unit fixedly mounted in the housing, the heater unit comprising means for radiating heat into the environment about the heater unit; and a heating element arrangement confined within the heater unit.
In another aspect of the invention, there is provided a heater unit for use in an electric heater, comprising: a heat conductive tube having an interior surface and an exterior surface; an electrical heating element arrangement contained within, and in thermal contact with, the interior surface of the heat conductive tube; and a plurality of heat radiating fins arranged along, and in thermal contact with, the exterior surface of the heat conductive tube.
Variations of physical construction parameters are possible without departing from the basic concepts of the present invention. For example, instead of providing a single central heat conductive tube, a plurality of such tubes may be provided, and additional metal fins may be provided to interconnect the plurality of tubes for improved heat radiation and distribution.
Various geometric shapes for the overall configuration of the heater unit are likewise possible, the preferred configuration being an elongated linear central heat conductive tube, or tubes, from which two sets of thin, spaced apart metal fins extend in a V shape as viewed from one end of the heater unit, the fins making an angle of approximately 90 degrees.
It is to be understood that any number of central heat conductive tubes can be employed, any shape for the heat conductive tube(s) including curved and angled shapes, and any number of heat radiating metal fin arrangements can be fitted to associated heat conductive tubes, and any overall geometrical shape and cross section for the heater unit, or units, are possible, consistent with the improved heater and heater unit concepts and aspects according to the present invention.
Compared with prior art heaters of similar usage, the heater, or heater unit, of the present invention exhibits a number of advantages:
a. a high heat transfer rate, due to the choice of materials, construction design, and large surface area for heat radiation;
b. mechanically very robust, due to unitary, single cast construction;
c. a safe surface condition, due to full confinement of electrical heating element, and uniform heat distribution with the aid of one or more heat radiating metal fin arrangements maintaining surface temperatures to under 400xc2x0 C.;
d. a relatively long life, due to protection of a confined heating element from excessive oxidation and inadvertent mechanical damage by the user;
e. excellent insulation characteristics, due to the use of a heating element arrangement which includes a heater element, insulation surrounding the heating element, and a heat conductive body surrounding the insulation; and
f. highly water resistant, due to inaccessibility of the heating element through which current flows to produce heat energy.